Federal Reserve Chairman Ben S. Bernanke endorsed government efforts to stimulate the economy yesterday, as congressional leaders and the Bush administration moved closer to agreement on a plan.

President Bush plans to lay out the principles behind his preferred stimulus today, although he will not provide details. The leading ideas in the administration are to give rebates of up to $800 to each taxpayer and introduce tax incentives for business investment, but administration officials said no decision has been made on exactly what to do to try to prevent a recession.

House Speaker Nancy Pelosi (D-Calif.) said Congress will have a package ready for action by Jan. 28, when Bush delivers his State of the Union address. House Republicans backed away from their demand that Bush's tax cuts be made permanent, which would have been a deal-killer for Democrats. Some tension between the administration and congressional leaders remained, though, as Senate Majority Leader Harry Reid (D-Nev.) sharply criticized Bush for talking about his stimulus plans prematurely.

While consensus was forming in Washington, yesterday was another painful day on Wall Street. The Dow Jones industrial average fell 306.95 points, or 2.5 percent, as Merrill Lynch reported a huge quarterly loss and a report indicated that U.S. housing starts fell 14.2 percent from November to December.

Bernanke, in testimony to the House Budget Committee, seemed to repudiate those in Congress who seek to use economic stimulus to put in place policies that would affect the economy over the longer term -- permanent tax cuts, for example, or big infrastructure projects. Bernanke explicitly and repeatedly urged Congress not to conflate policy changes that might make sense in the long run with those that would provide immediate help for the economy.

"Fiscal stimulus that comes too late will not help support economic activity in the near term, and it could be actively destabilizing if it comes at a time when growth is already improving," Bernanke said. He added later, "I think in order for this to be effective you need to move very quickly."

Bernanke has been reluctant to take on the role his predecessor, Alan Greenspan, played as the nation's economist-in-chief. Greenspan often told Congress of his economic policy preferences, but Bernanke yesterday repeatedly declined to take positions on what tax and spending levels are appropriate. ("Does Congress spend to much?" asked Rep. J. Gresham Barrett (R-S.C.). "That's not my call," Bernanke said.)

The Fed chairman did state some principles for what kinds of policies would do the most to keep the economy from slowing too drastically in 2008. He called the stimulus packages being considered, $50 billion to $150 billion, "reasonable." And he indicated that money provided to low- and moderate-income Americans is likely to result in more new economic activity than funds that go to people with high incomes.

Congressional leaders appeared to heed the advice about separating long-term economic policy from short-term stimulus. Pelosi emphasized, after a conference call with Bush, that Congress and the administration were working on a proposal that will be "timely, targeted, and temporary," which is consistent with what Bernanke advised in his testimony.

"We'd rather keep this as plain vanilla as we can," Budget Committee Chairman John M. Spratt Jr. (D-S.C.) told reporters.

Republican leaders, meanwhile, indicated that they could go along with a stimulus plan that does not include a permanent extension of Bush's first-term tax cuts, which are to expire in 2011.

"They've drawn a line in the sand on the Bush tax-cut extension, so we've seen a shift," said Rep. Eric Cantor (Va.), the Republicans' chief deputy whip. "There's been a realization that we need to get something done, and the expectations are not that high that we will get that done."

A senior House Democratic leadership aide said Pelosi was willing to greet the Republican offer to drop the demand to make Bush's tax cuts permanent with a concession of her own, acceptance of a significant business tax cut to encourage investment.

And House Ways and Means Committee Chairman Charles B. Rangel (D-N.Y.) vowed to reach an agreement with congressional Republicans and Bush on economic stimulus, snubbing his presidential candidate, Hillary Rodham Clinton, in the interest of bipartisanship.

In an interview with washingtonpost.com's PostTalk, Rangel dismissed the stimulus proposals of all of the presidential candidates, suggesting in particular that Clinton could be useful in the debate only if she could influence the tax-writing Senate Finance Committee, on which she does not sit, or that committee's ranking Republican, Charles E. Grassley of Iowa. "This is a time where no one can afford to be partisan," Rangel said.

White House spokesman Tony Fratto said: "The headwinds that we're dealing with right now are things that we see over the next coming quarters. So we do want to try to pass something quickly." He added, "I see no obstacle to that. It seems to me that both sides of the aisle and both Houses of Congress want to try to get to an agreement."

Not everyone was getting along, however. During the conference call with Bush, Reid was angry when he heard that Bush was going to go public today with his stimulus proposals, demanding to know why the president was not waiting for a bipartisan plan. Others on the conference call had to calm Reid down, according to congressional sources, and Bush reassured him that he would be announcing only his "principles" for stimulus, not a plan.

"I am disappointed that [Bush] is rejecting a request from leaders of both parties and both chambers to work with us directly to develop a bipartisan package rather than unilaterally detailing his own approach without congressional input," Reid said in a written statement.

On the Republican side, Cantor disparaged Democratic proposals to extend and expand unemployment insurance, temporarily boost the federal share of Medicaid payments, and offer cash to states hit hard by the housing crisis.

"Those are enhancements of the safety net in a very uncertain time," Cantor said. "I'm not saying that's not a worthy goal, but if we are in pursuit of stimulus, this is not what we're looking for."